Thin flat panel led luminaire

ABSTRACT

The invention described herein is a very thin flat panel LED luminaire, including a flat baseboard, a flat reflection panel, a flat acrylic panel, a flat diffusion panel, LED bar, and aluminum encasement frame which combines with the baseboard to form the chassis for the luminaire. The LED bar is placed along either or both sides of the stack. The acrylic panel is printed with a mesh-like mask pattern of dots in a pattern in which the density of the pattern is decreases the farther away from the LED bar the pattern is, differentially coupling the light from the point source LED bar from the reflection panel into the flat acrylic panel so that illumination across the luminaire is substantially uniform.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority from People's Republic of ChinaApplication No. 201120147703,9, filed May 11, 2011, incorporated hereinby reference in its entirety.

BACKGROUND

Field of the Invention

The present invention is related to the application of the LightEmitting Diode (“LED”) light source to form a very thin LED flatluminaire for general indoor and outdoor lighting purposes. Theluminaire, specifically, reflects and diffuses light from an LED lightsource which is installed along the edges of the very thin lightstructure. The light rays are diffused in a manner that provides uniformillumination and color temperature across the luminaire such that thereis no irritation from directly looking at the light source.

Description of the Related Art

LED technology provides for the manufacture of light fixtures that offerhigh lumen illumination, low energy consumption, and extended life cyclecompared to traditional lighting sources such as fluorescent orincandescent light bulbs. However, in current applications of LEDtechnology for general lighting purposes, the LED light source isarranged so that the LED light provides illumination directly to thearea/space requiring light. This results in glare which may beuncomfortable to the eyes when the LED light source is looked atdirectly. Another current application of LED lighting technology uses anLED light source to illuminate the backside of a display board todisplay graphics and/or textual information to a user. In this approach,the displaying material acts to diffuse the light from the LED lightsource.

Another approach which incorporates a reflection or diffusion panelincluding a plurality of tiny humps distributed across the panel hasalso been used in an attempt to diffuse light from and LED sourcearranged along the side of the luminaire. This approach utilizesinternal reflections within the bumps to spread the light over thesurface of the luminaire. However, the usage of such a structure resultsin increased complexity of manufacture, and increased thickness of theluminaire.

What has been needed, and heretofore unavailable, is a thin, easilymanufactured luminaire that provides uniform illumination across thesurface of the luminaire. Such a luminaire would be side lit by one ormore LED light sources, yet be thin, reliable, and easy to manufacture.The luminaire would be configured to (i) reflect the sharp light raysdirectly emitting from the LED light source and (ii) distribute thelight rays uniformly to the space without compromising the amount oflumens provided by the luminaire. Furthermore, the resulting light raysfrom the luminaire should provide a comfortable lighting experience.

SUMMARY OF THE INVENTION

In its most general aspect, the invention provides a very thin LED flatluminaire having a simple structure that provides uniform lightdistribution without glare and visually comfortable lighting. Theluminaire generally includes a flat baseboard, a flat reflection panel,a flat acrylic panel, a diffusion panel, a bar with multiple lightemitting diodes inlaid in the bar (“LED bar”) and an aluminum encasementframe.

In one aspect, the luminaire device is assembled by stacking of thebaseboard and panels. The order of the assembly from top down is thebaseboard, the reflection panel, the acrylic panel, and the diffusionpanel. The LED bar is positioned on either side, or both sides of thestack. The LED light source on the bar faces toward the stack. Thealuminum encasement frame clamps the stack together with the LED barinside of the encasement frame. The encasement frame is screwed togetherwith steel joiner to form the chassis for the entire luminaire device.In alternative aspects, two types of joints have been designed betweenthe encasement frame and the baseboard. One aspect includes an “U” shapeencasement frame clamped onto the baseboard and the diffusion board. Theother aspect is an “L” shape encasement frame with the baseboard screwedonto the encasement frame edge. In other aspects, a transformer isprovided to convert 110/220V alternating current to the appropriatedirect current application for the size of the luminaire.

In another aspect, the acrylic panel is printed with black dots in amesh-like pattern on one side. The size of the dots and the thickness ofthe mesh connecting the dots is larger, resulting in a less densepattern farther away from the LED light bar that couples more light fromthe reflection panel into the acrylic panel farther away from the LEDlight bar; the size of the dots is smaller, as is the thickness of themesh connecting the dots closer to the LED bar, resulting in a denserpattern that couples less light from the reflection panel into theacrylic panel closer to the LED bar. This mesh-like pattern thusprovides for a uniform transmission of light across the area of theacrylic panel into a diffusion panel for illuminating a space. Theprinted pattern is determined by the shape and size of the luminaire,area of the light emitting surface, and wattage of the light emittingdiodes.

In yet another aspect, the printed pattern is designed with strictoptical science through proprietary computer applications. This printedpattern “filters” the light intensity to achieve uniform lightdistribution.

In yet another aspect, the LED bar is positioned to emit light to theedge of the flat reflection panel. The flat reflection panel thenreflects the light to the acrylic panel. The acrylic panel has amesh-like pattern of dots across the face of the acrylic panel, thedensity of the dots and mesh being adjusted in such a manner that thelight transmitted by the reflection panel into the acrylic panel hasbeen filtered for uniform evenness through the acrylic panel. Thus, theintensity of the light being emitted by the acrylic panel is relativelyuniform across its face. Once the light is filtered through the acrylicpanel, the light passes through the diffusion panel which is, in oneaspect, an optical polypropylene material that has been treated toprovide a magnifying effect. The diffusion panel may further amplify anddistribute the light uniformly to the space to be illuminated, resultingin a soft and warm light which is comfortable to the human eye.

In still another aspect, the device is a symmetrical shape, such as asquare or rectangular; however, in alternative aspects, asymmetrical, orirregular shapes can also be made.

In yet another aspect, the present invention includes a thin LED flatluminaire, comprising: a LED bar having at least one light emittingdiode disposed thereon; an optical stack having an edge that abuts theLED bar, including, from top to bottom, a flat baseboard, a flatreflection panel for receiving light from the LED bar, a flat acrylicpanel having a top surface and a bottom surface, the top surface facingthe flat reflection panel, the top surface having a mask pattern printedthereon, the mask pattern for filtering light transmitted from the flatreflection panel into the flat acrylic panel for providing a uniformtransmission of the light from the acrylic panel across the bottomsurface of the flat acrylic panel, and a flat diffusion panel configuredto receive the light from the bottom surface of the flat acrylic paneland emit the light into a space to be illuminated.

In another aspect, the present invention also includes an encasementframe clamped .onto the stack and fastened together at each corner withcorner joiners.

In still another aspect, the mask pattern is printed with meshing dots,the printed pattern of meshing dots being less dense farther from theLED bar light source and more dense closer to the LED light source so asto selectively filter more light closer to the LED light and less lightfather from the LED light source to provide for uniform transmission oflight from the acrylic panel across the bottom surface of the flatacrylic panel.

In yet another aspect, the printed meshing dot pattern is determined bythe shape and size of the luminaire, area of the light emitting surface,and wattage of light emitting diodes. In another aspect, the mask filteris printed using black ink.

In another aspect, the diffusion panel is an optical polypropylene panelmanufactured with magnifying capability to provide optimal distributionof light, and in still another aspect, the diffusion panel is treated totransmit light with a selected warmth and color characteristic.

In a further aspect, the mask pattern is generated by a printercontrolled by a computer programmed with software commands to generate apattern in accordance with the equation:

${f(j)} = \frac{a}{\sqrt{1 + {\frac{\left\lbrack {\left( \frac{a}{b} \right)^{2} - 1} \right\rbrack}{180^{2}}\left( {j - 180} \right)^{2}}}}$

where a is the ratio of dot density in the center of a light area of theacrylic panel, and j is the ratio of dot density near the LED bar.

Other features and advantages of the invention will become apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings, which illustrate, by way of example, the featuresof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of a thin LED flatluminaire, looking at the light emitting face of the device.

FIG. 2 is a perspective view of the embodiment of FIG. 1 showing theluminaire from the backside.

FIG. 3 is a cross-sectional view of the embodiment of FIG. 2 asindicated by line A, illustrating the various components of theluminaire.

FIG. 4 is a cross-sectional view of the embodiment of FIG. 2 asindicated by line B, illustrating the components of the luminaire.

FIG. 5 is a top view of one embodiment of the acrylic panel of FIG. 3,showing the distribution of a pattern printed onto the acrylic panel forreflecting light produced by an LED bar to provide uniform distributionof the light across the illuminating area of the luminaire.

FIG. 5A is an enlarged cross-sectional view of a portion of the acrylicpanel of FIG. 5, showing how light is reflected by particles of varyingsize embedded within an ink layer that has been applied to the acrylicpanel.

FIG. 6 is an enlarged view of a corner of the embodiment of FIG. 2.

FIG. 7 is a perspective side view of one embodiment of the LED barillustrated in FIG. 2.

FIG. 8 is a perspective side view the embodiment of the LED bar of FIG.7 showing the interface of the LED bar and the various panels of theluminaire.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings in detail, in which like referencenumerals indicate like or corresponding elements among the severalfigures, there is shown in FIG. 1 an exemplary thin flat luminaireconstructed in accordance with principles of the present invention.

Thin flat luminaires of the type illustrated in FIG. 1 are useful inproviding light in a more efficient manner than can be accomplishedusing prior art florescent fixtures. Such fixtures are commonly used inpublic spaces, and may take the form of square or rectangular fixtures.Common sizes of such fixtures are four feet by two feet, and two feet bytwo feet. Other sizes and shapes axe also possible.

Light Emitting Diodes, or LEDs, are highly efficient sources of lightwhose mean time between replacement is also significantly greater thanflorescent or incandescent light sources. LEDs however, are typicallyrelatively small in size, and thus provide light that is relativelyintense and focused within a small area.

The various embodiments of the present invention incorporate LEDs toprovide light, but then provides a structure that disperses the lightuniformly over the entire area of the luminaire fixture. To accomplishthis, as will be discussed in more detail below, the LED light isreflected and diffused in a manner which provides for a relativelyuniform emission of light from the surface of the luminaire.

As seen in FIG. 1, in one embodiment, the luminaire 10 includes anencasement frame 15 that is used to hold a number of panels inalignment. FIG. 1 is a view looking at the light emitting surface of theluminaire 10, which is defined by a diffusion panel 20. The encasementframe includes a number of elongated structural members 35, 40, 45 and50 which may form a square or rectangle, depending on the relativelengths of the various elongated structural members. For example, wherethe length of elongated structural members 35, 40, 45 and 50 are equal,a square luminaire results. Similarly, where elongated structuralmembers 40, 50 are longer than members 35, 45, a rectangular luminaireis formed.

FIG. 2 and FIG. 6 illustrate details of the construction of theencasement frame 15. Elongated structural members 35 and 40 are joinedusing a fitting 55 that forms a corner joint. Fitting 55 is an elongatedmember having bent into a right angle (90 degrees) to form the corner.The right angle may be sharply defined, or it may have a radius tosoften the shape of the corner for safety and aesthetic purposes. Whenbent into a right angle in this fashion, fitting 55 has a pair of wingsthat are used for reinforcing the corner of the encasement frame, andalso provide a foundation for attaching the elongated structural memberstogether.

When placed between two of the elongated structural members, each wingof fitting 55 extends from an edge of the structural member for adistance along the longitudinal axis of the structural member. At leastone screw 30 is used to fasten the elongated structural member 35, 40 tothe fitting 55 to join the elongated structural members together.Fitting 25 may be formed of steel or any other suitable material. Acorner joiner 25 may also be used to fill any gap that occurs betweentwo elongated structural member if necessary to provide an aestheticallypleasing corner joint. As will be apparent to those skilled in the art,other designs and shapes for the encasement frame may be used, and arecontemplated as being within the scope of the present invention.

Also visible in FIG. 2 is a baseboard 60 which fonrus the back of theluminaire. Power is provided to the LED light source or sources withinthe luminaire using a wire 65. Depending on the installation of thepanel, the panel may be wired directly to a power source, oralternatively, an electrical plug 67 may be provided. A transformer 70is also provided between the plug and the LED light source to reduce thevoltage from the power source to a voltage that is required to operatethe LED light source. Additional circuitry may be included to transformthe alternating current into direct current if required by the LED lightsource.

The encasement frame may be formed from materials such as steel oraluminum provided it can rigidly support the components of theluminaire. For example, in one embodiment, the encasement frame isformed from an aluminum alloy material such as AL6063. The encasementframe maybe coated with vinyl or other materials to provide an aestheticappearance.

FIG. 3 is a cross-sectional view of an embodiment of the luminaireshowing the arrangement of the components contained within theencasement frame 15 that provide the light that is emitted from thediffusion panel 20 (FIG. 1). As shown in this figure, encasement frame15 holds a baseboard 60, a reflection panel 75, and acrylic panel 80,and a diffusion panel 20 in a stacked arrangement, with the baseboardforming a backside of the luminaire, and the diffusion panel forming thelight emitting surface of the luminaire. A LED bar 85 abuts one edge ofthe stack of panel, transmitting light into the edge of the reflectionpanel 75. Note that the LED bar 85 does not illuminate the diffusionpanel 20 directly, and thus light emitted from the bottom surface of thediffusion panel is not emitted directly from the LED bar. Thiseliminates the potential discomfort or harm resulting from directlyviewing the intense light produced by the LED bar. In an alternativeembodiment, a second LED bar 85′ may also be used, located on theopposite side of the stack from LED bar 85 where necessary to providesufficient light to the stack to provide a sufficient amount ofillumination from the bottom surface of the diffusion panel.

The baseboard 60 is typically formed from an opaque material havingsufficient structural rigidity to stabilize the assembly when theluminaire is installed. In one embodiment, galvanized steel sheetapproximately 0.500 millimeters in thickness has been found to besuitable, but other thicknesses and materials may be used depending onthe design and functional requirements of the particular size or shapeof the luminaire.

The LED bar is positioned so that it emits light into the edge of theflat reflection panel 75. The light transmitted into the edge of thereflection panel is reflected within the thickness of the panel in amanner well known to those skilled in the art, and, as will be describedin more detail below, is ultimately coupled out of the reflection paneland into the acrylic panel 80.

In one embodiment, a filter mask having a mesh-like pattern is folioedon the top surface of the acrylic panel 80. This mesh-like patternserves to differentially couple light from the reflection panel into theacrylic panel in such a way that the light being emitted from the bottomsurface of the acrylic panel into the diffusional panel 20 has a uniformintensity across the area of the bottom surface of the acrylic panel 80.

The diffusion panel 20 may further amplify and distribute the lightunifou dy to the space to be illuminated. As will be discussed morefully below, the diffusion panel may also be treated to change the colortemperature of the light to enhance the warmth and color of theillumination as desired.

In one embodiment, the LED bar 85, 85′ is a metal core printed circuitboard. The sizing and luminosity of the LED bar is selected dependingupon the requirements of the final luminaire. Other designs for an LEDbar may be used as dictated by the design requirements of the luminairewithout departing from the contemplated scope of the invention.

The reflection panel 75 is preferably formed of polyethyleneterephthalate (“PET”) which is a thermoplastic polymer resin that hasreflective and opaque properties and, in one embodiment, isapproximately 0.188 millimeters in thickness. The purpose of thereflection panel is to provide a medium to reflect light rays from theLED bar onto the top surface of the acrylic panel 80.

The acrylic panel 80 may be formed from poly(methyl methacrylate)(“PMMA”), commonly known as acrylic glass. In one embodiment, theacrylic panel is approximately 3.00 millimeters in thickness. As statedpreviously, a mesh-like mask pattern is applied to the top surface ofthe acrylic panel. This pattern is typically applied in a manner whereinthe density of the pattern decreases as the distance across the panelincreases in relation to the LED bar so as to couple more light from thereflection panel into the acrylic panel the farther away from the LEDbar. This pattern filters the intensity of the light rays coupled intothe acrylic panel 80 by the reflection panel 75 so as to achieve auniform light distribution across the emitting surface of the luminaire.

The diffusion panel 20 is typically formed of optical polypropylenematerial, which, in one embodiment, is approximately 1.500 millimetersin thickness. This panel diffuses the light to the space with evendistribution providing warmer light rays which are visually comfortableto the human eye.

FIG. 4 is a further illustration of the arrangement of the panels withinthe encasement frame. This view is rotated 90 degrees from the viewshown in FIG. 3, and thus the LED bars 85, 85′ are not visible.

Referring now to FIGS. 5 and 5A, a mask pattern 100 that is applied tothe top surface of the acrylic panel 80 will now be described. Since thelight from the LED bar is transmitted into the edge of the reflectionpanel 75, the distribution of light across the width of the reflectionpanel is not uniform. One skilled in the art will immediately understandthat the intensity of light available to be coupled into the acrylicpanel immediately adjacent the LED bar is far greater than the intensityof light available at a point (or area) farthest from the LED bar. Thus,if no mechanism is used to adjust the intensity of light transmittedthrough the acrylic panel, the light emitted by the diffusion panel intothe space to be illuminated would not be uniform. In other words, if onelooked at such a luminaire, the luminaire would appear brightest at theedge where the LED bar is located, and would be dimmest at the farthestdistance across the luminaire from the LED bar. Such a result is notacceptable for aesthetic and functional reasons.

To address this problem, and to ensure uniformity of illumination acrossthe emitting surface of the luminaire, a mesh-line mask filter isapplied to the top surface of the acrylic panel 80. In one embodiment,the mask filter is formed by printing the pattern on the acrylic panelusing an ink that is composed of titanium dioxide (TiO₂) and bariumsulfate (BASO₄). Other inks may be used that satisfy the requirementsthat will be discussed in more detail below. It is important that theindex of refraction of the components of the ink cooperate with theoptical properties of the acrylic material of the acrylic panel suchthat the light within the panel is reflected or deflected in a mannerthat ensures the light is evenly distributed across the acrylic panel.

As discussed previously, the acrylic panel is preferably formed of PMMA,which has a refractive index of 1.49 (25 degrees Celsius). This resultsin a reflection angle within the acrylic panel of 42.2 degrees. When thereflection angle is less than 45 degrees, light traveling in a specificdirection within the panel can be reflected numerous times within thepanel, providing for dispersion of the light throughout the panel.

The mask filter alters the coupling of light from the reflection panelinto the acrylic panel, constructively and destructively interferingwith the light in a manner that provides for uniform emission of thelight from the bottom of the acrylic panel. To accomplish this, thedensity of the mask filter must change depending on the distance of aparticular point on the acrylic panel from the light source (LED bar 85,85′). As shown in FIG. 5, the density of the mask pattern 100 is mostdense at points closes to LED bars 85, 85′, and least dense in themiddle of the panel, which is the farthest portion of the panel awayfrom LED bars 85, 85′.

The mask filter may take the form, for example, of a mesh ofinterconnected dots. In the middle of the panel, the radius of the dotsis large, and the mesh connecting the dots is also thicker. This resultsin a reduced density of the pattern, allowing more light to be coupledinto the acrylic panel from the reflection panel. The closer to thelight source, the smaller the radius of the dots is and the thinner themesh is, resulting in a denser pattern that allows less light to becoupled into the acrylic panel. In this arrangement, the closer to thelight source, the less light is reflected or deflected in order to evenout with the light intensity at the farther away area.

The mask filter is designed in such a manner so as uneven light emittingfrom the luminaire is not visible to the human eye. To accomplish this,it is important to minimize the overlay of dots in the filter. In oneembodiment of the present invention, dot overly is minimized utilizing amethod called Low Discrepancy Sequences (LDS).

If the gap between dots is N, and the gap is desired to be closed withinan allowable variance, D_(N), the follow formula can be used:

$\begin{matrix}{{D_{N}({LDS})} \leq {C\frac{\left( {\log \; N} \right)^{2}}{N}}} & {{Equ}.\mspace{14mu} 1}\end{matrix}$

where C is a constant and has no relation to N dots, and D_(N) isdefined by 0≦x, y≦1.

Thus, D_(N) can be calculated as:

$\begin{matrix}{D_{N} = {\begin{matrix}\sup \\{\left( {x,y} \right){e\left\lbrack {0,1} \right\rbrack}^{2}}\end{matrix}{{\frac{\# {E\left( {x,y} \right)}}{N} - {xy}}}}} & {{Equ}.\mspace{14mu} 2}\end{matrix}$

where x, y is the vector of (0,0) and (x,y).

The vector divides the dots within the area. N is the entire dot count.The absolute number derived from the formula is the difference betweenthe percentage of the dots and the percentage of the area. When the dotsare getting very dense, the number is near 0; therefore it representsthe variation of the dots. This avoids sporadic spread of the dots,

Even though the LDS design results in an even spread of the dots in themesh, the diameter of the dots is limited, therefore overlap of the dotsmay still occur. In order maintain a distance between the dots, it isnecessary to apply a further dynamic theory to determining the positionof the dots. In this method, it is assumed that the dots will react witheach other, and that reaction results in a repulsive force between eachof the dots.

Assuming that dot i and dot j result in repulsive force, and assumingthat the positions of dots designed by the LDS method are the initiallocation calculated as shown below:

$\begin{matrix}{{{f_{ij}m\frac{d^{2}r_{i}}{{dt}^{2}}} + {c\frac{{dr}_{i}}{dt}}} = {F_{i} = {\sum\limits_{j}^{\;}f_{ij}}}} & {{Equ}.\mspace{14mu} 3}\end{matrix}$

where m and c are constants, Assuming t₀ to be an initial time, thet>t₀:

$\begin{matrix}{{r_{i}(t)} = {{r_{i}\left( t_{0} \right)} + {\frac{1}{c}{\int_{t_{0}}^{t}{{dt}^{\prime}{F_{i}\left( t^{\prime} \right)}\left\lceil {1 - {\exp \frac{c\left( {t - t^{\prime}} \right)}{m}}} \right\rceil}}}}} & {{Equ}.\mspace{14mu} 4}\end{matrix}$

Based on Equ. 4, assuming unlimited repulsive forces between dots, suchthat the final balance of the reactions becomes 1, the dot location canbe calculated as:

$\begin{matrix}{{{r_{i}\left( {t + {\Delta \; t}} \right)} - {r_{i}(t)}} = {\frac{1}{c}\Delta \; {{tF}_{i}(t)}}} & {{Equ}.\mspace{14mu} 5}\end{matrix}$

The LDS design results in an even spread of dots, and is more efficientthan other methods, such as apply a fuzzy logic algorithm. Furtherefficiency is obtained by applying both LDS and repulsive force methodsto dot pattern design.

In most circumstances, then, the following equation may be used todesign the dot pattern:

$\begin{matrix}{{f(j)} = \frac{a}{\sqrt{1 + {\frac{\left\lbrack {\left( \frac{a}{b} \right)^{2} - 1} \right\rbrack}{180^{2}}\left( {j - 180} \right)^{2}}}}} & {{Equ}.\mspace{14mu} 6}\end{matrix}$

where a is the ratio of dot density in the center of the light area, andj is the ratio of dot density near the light source.

The pattern designed using these methods will vary depending on theshape and size of the luminaire, the area of the light emitting surfaceand the wattage of the fixture. As described above, the acrylic panel 80is positioned in the stack such that the printed pattern faces thereflection panel 75, that is, the dots are printed on the top of theacrylic panel.

Once the light rays are filtered by the acrylic panel 80, the light raysare directed through the diffusion panel 20, which amplifies the lightand distributes the light evenly to the space to be illuminated. Thediffusion panel also softens the light in such a manner that the lightappears warmer and is more comfortable to the human eye. In someembodiments, the diffusion panel may also be treated or coated toprovide a magnification effect. In still other embodiments, the colorand surface texture of the diffusion panel may be varied according tothe customer's requirement for the color of the light and for aestheticappearance.

Referring again to FIGS. 2 and 6, the assembly of the stack and the LEDbar is achieved by the encasement frame which may be a prefabricatedaluminum alloy in the cross-sectional shape as shown in FIG. 3. In orderto achieve the maximum durability, the ninety degree corner may beformed by a corner joiner 25 connecting to two straight pieces ofaluminum. The corner joiner may be made of plastic, aluminum, or othersuitable material. This corner transition is tighter and more attractivethan fabricating bent corners from a continuous piece of aluminum alloy.As illustrated in FIG. 6, the encasement frame 15 is fastened withscrews 30 to a ninety degree steel joiner 55 in the middle of thealuminum alloy encasement frame. At each corner there is an area withthe corner joiner connecting the straight aluminum pieces outside of theframe. For durability and aesthetic appearance, there is a ninety degreesteel joiner in the middle of the aluminum alloy encasement frame toreceive the fastening screws. All three parts, aluminum alloy encasementframe, corner joiner, and steel joiner, are fastened together with thescrews from the side of the aluminum alloy encasement frame.

FIG. 7 is a perspective side view of one embodiment of a LED barsuitable for use in the luminaire of the present invention. In thisembodiment, LED bar 200 includes a structural member 205 in the form ofan elongated strip upon which are mounted a plurality of light emittingdiodes 210. Electrical wire leads 215 provide electrical power of theproper voltage and type (alternating or direct current) to the lightemitting diodes. In some embodiments, chip resistors 220 may also beused to ensure proper operation and reliability of the light emittingdiodes.

FIG. 8 is a perspective side view illustrating how the stack of panelsaligns with the LED bar 220 of FIG. 7. In this embodiment, baseboard 60,reflection panel 75, acrylic panel 80 and diffusion panel 20 are stackedupon each other and then positioned so that an edge of the panels abutsthe LED bar 220. Light from the light emitting diodes 210 is transmittedinto the edges of the reflection panel, the edges of the acrylic paneland diffusion panel being opaque or otherwise rendered non-receptive tothe light from the LED bar so that no light from the LED bar is receivedinto the edges of the acrylic and diffusion panels and thus is notpropagated throughout those panels.

The mask pattern may be printed on the acrylic panel using variousmethods. For example, in one method, the surface of the acrylic panelfacing the reflection panel is polished until shiny. The dot pattern isfirst engraved on a sheet with holes penetrating through the sheet toallow passage of ink through the sheet. The sheet is then laid upon theshiny surface of the acrylic panel, and the ink is applied. The acrylicpanel is then placed into an oven to dry the ink. This method, however,may result in low quality, because the ink may not be able to flowthrough very small holes in the sheet, thus printing a pattern that maynot provide optimal filtering of the light as it is transmitted into theacrylic panel.

Another method uses a laser printer to print ink to form the maskpattern directly on the shiny surface of the acrylic panel. The laserprinter is controlled either by a specialized computer designed togenerate the dot patterns in the method described above, or iscontrolled by a general computer operating under the control of softwarecommands specifically designed to operate the computer to carry out thegeneration of the patterns in accordance with the Methods of the presentinvention. The mask pattern may be generated all at once, saved, andthen used to control the laser printer to print the pattern onto theacrylic panel, or the mask pattern may be printed as it is generated bythe computer. Other methods of printing the patterns in accordance withthe present invention may also be used, as long as they provide highquality patterns capable of providing a uniform dispersion of the lightreceived from the reflection panel to the acrylic panel.

In its various embodiment, luminaires in accordance with the principlesof the present invention can be adapted for all indoor lightenvironments, including, but not limited to, ceiling mount, T-Bar trackmount, suspension, and enclosure by other construction materials withequivalent safety characteristics. Screws can also attach suspensionclips or loops to the encasement frame. These loops are used to connectto a support system in an open ceiling environment.

While several particular kilns of the invention have been illustratedand described, it will be apparent that various modifications can bemade without departing from the spirit and scope of the invention.

I claim:
 1. A thin LED flat luminaire, comprising: a LED bar having atleast one light emitting diode disposed thereon; an optical stack havingan edge that abuts the LED bar, including, from top to bottom, a flatbaseboard, a flat reflection panel for receiving light from the LED bar,a flat acrylic panel having a top surface and a bottom surface, the topsurface facing the flat reflection panel, the top surface having a maskpattern printed thereon, the mask pattern for filtering lighttransmitted from the flat reflection panel into the flat acrylic panelfor providing a uniform transmission of the light from the acrylic panelacross the bottom surface of the flat acrylic panel, and a flatdiffusion panel configured to receive the light from the bottom surfaceof the flat acrylic panel and emit the light into a space to beilluminated.
 2. The thin LED flat luminaire of claim 1, furthercomprising: an encasement frame clamped onto the stack and fastenedtogether at each corner with separate corner joiners.
 3. The thin LEDflat luminaire of claim 1, wherein the mask pattern is printed withmeshing dots, the printed pattern of meshing dots being less densefarther from the LED bar light source and more dense closer to the LEDlight source so as to selectively filter more light closer to the LEDlight and less light father from the LED light source to provide foruniform transmission of light from the acrylic panel across the bottomsurface of the flat acrylic panel.
 4. The thin LED flat luminaire ofclaim 3, wherein the printed meshing dot pattern is determined by theshape and size of the luminaire, area of the light emitting surface, andwattage of light emitting diodes.
 5. The thin LED flat luminaire ofclaim 1, wherein the mask filter is printed using black ink.
 6. The thinLED flat luminaire of claim 1, wherein the diffusion panel is an opticalpolypropylene panel manufactured with magnifying capability to provideoptimal distribution of light.
 7. The thin LED flat luminaire of claim1, wherein the diffusion panel is treated to transmit light with aselected warmth and color characteristic.
 8. The thin LED flat luminaireof claim 1, wherein the mask pattern is generated by a printercontrolled by a computer programmed with software commands to generate apattern in accordance with the equation:${f(j)} = \frac{a}{\sqrt{1 + {\frac{\left\lbrack {\left( \frac{a}{b} \right)^{2} - 1} \right\rbrack}{180^{2}}\left( {j - 180} \right)^{2}}}}$where a is the ratio of dot density in the center of a light area of theacrylic panel, and j is the ratio of dot density near the LED bar.